The present invention relates to reinforced laminated composites and more particularly to the embedding of specially tailored short steel wires in a direction which will provide the optimum strengthening of the composite laminate against delamination.
In the field of naval aircraft structural development, it has been the general practice to reduce weight and cost and improve performance. In addition, as flight speeds increase and lift augmentation and thrust vectoring are utilized in vertical-short takeoffs/landing aircraft, high-temperature structures are required to withstand the effects of aerodynamic heating and hot exhaust gases. Significant achievements have been made in reducing structural weight by utilizing laminated composite materials such as graphite-epoxy, for temperature applications up to 450.degree. K. The advantages of graphite-epoxy laminates over conventional materials are well known as is evident from the increased utilization of graphite-epoxy in the aircraft industry over the last several years. An inherent weakness of graphite-epoxy laminates is their low interlaminar strength properties. These properties which include both shear and normal strength, reflect the characteristics of the low strength epoxy matrix material and do not exhibit the benefit of the high strength graphite fibers. For this reason, reinforced graphite-epoxy laminates such as shown in U.S. Pat. Nos. 4,109,435 and 3,837,985 have been developed for designs requiring high interlaminar strength. However, these reinforcement techniques are generally located in fixed patterns or along junctions without regard to specific requirements and local loadings. This results in excessive weight in aircraft components and higher costs.